1. Field of the Invention
The invention relates to motion transmitting devices with speed conversion and can be used for drives of general use machines and mechanisms. Said transducer relates to wave gears provided with intermediate members.
2. Description of the Related Art
The wave tooth gear is known (see “Reducers and motor—reducers of general use. engineering industry”. Reference book/L. S. Boyko, A. Z. Visockyi and others.—M: Mashinostroyenie, 1984, pp. 22–29; RU No. 2019760). In general this gear consists of three basic members, which are: rigid tooth wheel, flexible tooth wheel and wave generator. Said wave tooth gears having the high transmission ratio (up to 1:350 for one step), however have low efficiency caused by losses of energy to deformation of flexible wheel and to friction between engaged teeth.
Friction between engaged teeth and losses of energy to deformation of flexible wheel are eliminated in wave gear with intermediate members, which are rolling elements. Here, a file of rolling elements (balls or rollers) serves as a flexible wheel of traditional wave gear. Radial wave gears with intermediate rolling members are described in patents RU 2029167, RU 2029168, U.S. Pat. No. 5,989,144. In said gears the wave generator being a cam produces a wave of radial moving to a file of balls. Devices in which wave generator is eccentric rotating disc or idler located on crankshaft and driven in rotation by said crankshaft, also relate to this type of transducers. Eccentric rotating disc or idler in said devices has cam side surface formed as a tooth profile with a radial direction of teeth (patents U.S. Pat. No. 4,584,904, U.S. Pat. No. 4,643,047, U.S. Pat. No. 5,683,323). Said speed transducers like to all mechanisms with eccentric members have asymmetric loading to shaft thereby causing beating and the increasing deterioration of details unless to apply balancing elements. In axial wave transducers with intermediate members the wave generator forces a file of rolling members (balls) in an axial direction. Such transfers may refer to as differently and have some differences in their designs (SU 559052, SU 1025941). Their general disadvantage is that balls during operating periodically lose continuous rolling contact resulting in significant decreasing in operating efficiency.
There are known so-called Sinusoidal Ball Drives which also can be related to wave gears with intermediate members (Ignatishchev R. M. <<General Information on Sinusoidal Ball Drives>>, <<Bulletin of engineering industry>>, 1986, No. 2, pp. 24–28). In cited article designs of “two-sinusoidal” and “three-sinusoidal” gears are offered in which no whole cam participates in eccentric movement but only rolling bodies that considerably reduces asymmetric of loading. A motion transmitting unit of “two-sinusoidal” gear consists of three in series members. Two outer members provided with cam surfaces in form of a groove defined by periodic curve on an azimuth. The intermediate member has openings for balls and carries out the function of planet carrier and a separator simultaneously. One of members with a cam surface is the wave generator. The groove of the wave generator may be either singly-periodic or multiperiodic. Proportion of the cam surfaces periods are depending upon number of rolling elements and submitting to the certain law. This principle is realized both for radial and for axial wave transfers. For radial “two-sinusoidal” gear there are developed several specific kinematics. Periodic grooves with a radial direction of a bend are executed on flat surfaces of disks faced each other, and a cage is realized as a flat ring with radial slots is located between them (see also SU 1019148, Ignatishchev R. M., the Mogilyov machine-building institute, 30.04.88). Weight imbalance in such gear is reduced, and it matters only for gears with the high torque because of large ball sizes.
For axial “two-sinusoidal” gear there is developed one kinematics (see also SU 825823, the same applicant, 30.04.81). A motion transmitting unit comprises three coaxial nested members. Cam surfaces are executed as periodic grooves with axial direction of bend on lateral surfaces of external and internal members faced each other, and the intermediate member has through longitudinal slots.
To increase the gear ratio the same author had developed, so-called, “three-sinusoidal” gear with axial moving balls (SU 1216498, 07.03.86). Periodic in an azimuth direction grooves are formed in each of members. For this purpose the intermediate cage is connected to the housing since periodic groove on it is through circular groove.
The designs patented by firm Synkinetics, Inc.(U.S. Pat. No. 5,312,306, U.S. Pat. No. 5,514,045, WO 94/18472, U.S. Pat. No. 5,562,564, U.S. Pat. No. 5,600,699, U.S. Pat. No. 5,722,910, U.S. Pat. No. 5,954,615, U.S. Pat. No. 5,989,145, U.S. Pat. No. 6,039,672, U.S. Pat. No. 6,125,711) and also the patent of U.S. Pat. No. 5,577,423 relate to “two-sinusoidal” gears. In the above speed transducers is realized a principle sinusoidal—ball gear above described.
Thus, sinusoidal-ball gears have the following advantages: high reduction ratio with compact structure, simplicity of a design and small dimensions at the high torque. A principle of configuration of motion transmitting unit of the converter, fixed in a basis of all above described designs, is closest to the offered invention. But setting-up of described design configurations of three consistently located details limits number of constructive variants of performance since the intermediate detail, namely separator, necessarily should have through slots. In such design depth of grooves and thickness of the separator are approximately equal each other and are ⅓ of rolling body diameter. The analysis of loads exerted on a ball shows that the force acting on a ball from grooves do not pass through the center of a ball and consequently have two components: radial and axial, thus only one of them performs useful work, and another only increases losses of energy by friction. Furthermore the points of application of these forces are edges of grooves that do not allow realizing point-to-point contact of balls to grooves. It causes the raised deterioration of balls and destruction of grooves in their edges by transfer of the high torque. As marked in article (Pashkevich M. F. The bulletin of mechanical engineering, 1985, No. 7, pp. 23–26), the weakest on durability a part of sinusoidal-ball gear is a cage. Increasing its thickness is impossible because of the point of application of the force on a ball is displaced from the center toward edge and useful component of force is decreased.
As a prototype of gear with radial wave moving balls is chosen planetary three-sinusoidal gear (SU 1276869, 15.12.86) which represents the speed transducer realizing a principle of wave gear with intermediate rolling bodies. Torque transmitting unit of this speed transducer consists of three disks at least two of which are coaxially each other. One of disks is connected to the wave generator and is driving member in this gear. Each of disks has a cam surface in the form of closed periodic groove bent in a radial direction and continuously contacting balls. The grooves of two disks are located on the surfaces faced to each other, and the groove of intermediate disk is located on its side surface. In the one of embodiments, in order to decrease slippage of ball, the wave generator's disk is connected to shaft through crankshaft, and a groove on it is annular groove. Torque transmitting unit of this mechanism is not mass balanced since balls are on different distances from an axis of rotation. Unbalance is even more increased in embodiment with crankshaft; therefore it loses the general advantage of sinusoidal-ball gear. In order to obtain high loading abilities it is necessary to apply special means of mass balancing, such as special cut at the bottom of a groove (see SU 1511495, 30.09.89.) or a v-shaped slot in eccentric disk. Furthermore to this “three-sinusoidal” gear all conclusions concerning to points of the application of forces and to the raised deterioration of balls and to destruction of groves made above are fair. Later the design of this “three-sinusoidal” gear was modified, since it was found out, that balls while follow simultaneously between crests and hollows troughs along of three grooves may deviate from the average angular positions thus causing deterioration of dynamics and even jamming in driving engagement. In order to eliminate these disadvantages, addition thin-walled cage with radial slots is entered between disks of torque transmitting unit which cage fixes balls at equal angular spaces from each other while they passage the critical points (see Ignatishchev R. M. “Three-sinusoidal ball transfer the Bulletin of mechanical engineering”, 1987, 12, pp. 13–16). Such cage is no torque transmitting member, i.e. is non-loaded. At the same time, presence of the cage even more displaces points of application of forces acting to ball from an axis which pass through the centre of a ball, and thereby worsens distribution of forces.
It is an object of the present invention to provide a speed converter which is simplified in nature but is robust in transmission capability. It is a further object of present invention to provide speed converter design which is self-contained and multi-purpose similar to a bearing and which is adaptable to variety of situation. Invention results in development of the generalized basic design on basis of which it is possible to provide the various embodiments possessing general advantages: more compact and constructed of a minimum number of parts for its load rating, weight balanced, optimized load sharing among the torque transmitting elements, and also minimally possible useful volume of the torque transmitting unit allowing to use bearing seal and lubrication for life. On basis this design it is possible to develop a mechanism with the raised loading ability caused by of two-point contact of rolling bodies with grooves. The invention expands variety of designs and functions of wave gears thereby allowing to easily adapt the converter for any service conditions and to build it in the most various mechanisms. Speed converter according to the invention may carry out function of both a reducer and a multiplicator. Furthermore, speed reducer according to the invention is able to have with single input two ore more outputs or it is able to variable output in dependence of ratio of two inputs, and all these functions are realized in single torque transmitting unit, i.e. at one stage.